Slide-valve fob steam-engines



UNITED sTATEs PATENT oEEroEL RICHARD C. BRISTOL, OF CHICAGO, ILLINOIS.

SLIDE-VALVE FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 24,489, dated June 21, 1859; Reissued February 7,

To all whom it may concern:

. Be it known that I, RICHARD C. BRISTOL, of Chicago, in the county of Cookl and State of Illinois, have invented a new and useful l.

Similar letters of reference indicate like parts in all the drawings.

It is well known that the pressure of the steam upon a slide valve tends to produce a great amount of friction and various ydevices have been made known with a view to diminish this 'injurious effect. One of these has been to mount the slide valve upon four wheels, two upon each side, the parts being so proportioned that the rubbing face of the valve should just touch the cylinder face without pressing violently thereon. Such a device has been made more practicable by constructing the' valve in two parts, the back of the valve being one part and the face of the valve being another part, the wheels being attached to the back part only, and the two parts being fitted in steam tight contact each with the other, but with liberty to work relatively to each other like a piston and cylinder. These and all other previously known devices have accomplished the object but imperfectly. The presence of the wheels has necessitated an unusually capacious and in some instances an impracticably long steam chest. KThe friction and wear upon the axes of suchwheels has been also quite objectionable'. The operating of a separate cut-oifvalve, in the steam pipe, or on a plate extending across the steam chest above the slide valve, has been rendered less effective than usual by reason of the greater capacity of the steam chest, than with wheels.

the back of the main slide valve has been rendered completely impracticable until my Y fpartial rollers which are not subject to any vfriction upon their axes, neither do they compelany increase in the length of the steam chest. My partial rollers are cirvcular or cylindrical vthrough so large portions of their periphery as to allow the valve to travel thereon to the full extent rof its motion ;-the remainder of the periphery is reduced in diameter so that these partial rollers ymay be placed much nearer together and a much larger effective diameter thereof may be adopted as also a shorter steam These partial rollers are also guided and kept in position at or near their bearing points so that they 'are not like ordinary rollers liable to any possibility of displacement.

The nature of my invention consists .second in so arranging a cut-oif on the back of the supported 'part and so arranging suitable passages through both parts of the valve that the steam is conveyed to the cylinder ports through such passages alone with the usual effect due to expansive working, while the two parts of the valve may be allowed to work to a limited extent relatively to each other without involving a leakage of steam at the joints. As balanced ment ofthe parts ofrsuch valves has been heretofore produced by the pressure of the steam upon a certain portion not balanced. As the frictionof one part within the other is liable to be .very considerable it has in order to Vsecure a proper adjustment been necessary to leave a large portion of the faceated has produced a continuous friction between the valveeface and the cylinder-face. My .invention overcomes this difficulty vby causing a rigid union or unity of the two;

parts of the valves after the face-piece has assumed `the position proper for a tight cony .and Wit-hout producing any leak at the joint tact With the cylinder face.

To enable others skilled in the art to make 1 and use my invention I .will proceed to describei,-by .the aid .of .the [drawings-lle.

manner in which I construct Aandopferate it.

The valve proper is .constructed in .two portions A, 5B, :the latter .being itted steam tight into the former so .that it is adapted to slide vertically .therein to acer-tain extent,

as represented, Without allowing lsteam .tol pass through the joint. Set :screws .G C are provided by which the portions A B may be made to ahold ltheir relative places verytirmly Y if required. The fcut .off valve l) 11s ditted to slide AVsteani tight on the upper face of 'B :and is guided thereon `by led-ges or lips. The top of B .overhangs A :at `each side as represented andthe partial rollers E E which -are introduced between these overhanging portions and .the cylinder face M support B `on the circular portions of their -several periphenies,v and 'compel .it .to travel in .-a ,plane parallel to the face M. rllhe for-1n wiich l prefer for these partial rollers is ,shown in `Eig. VV1 and Fig. 2 a .part 'being shown .by strong and a part 'by .dotted lines ,in each ligure.'

The overhanging portion of B is made to inclose and .confine the :upper sides `or circular ends of .these 'partial rollers and the lower slidesor 'lower circular ends .thereof-` proper .extent Without touching the pins so long as the partial rollers ,are in their .correct positions 'but 4the :moment .one .olf lthe lpartial `rollers 'E becomes ,in any considerable degree displaced at either the top or the bottom it presses `the side o'f the corresponding slot against the ,pin -and .thus .prevents itself from becoming more displaced. Any lsensible displacement of eitherof the partial rollers alsofcauses one Yo .its straight edges to Imeet 'the `other straight edge :or 'to meet the side of the inclosure at each Vibration .and thus to aid in preventing it 4from becoming any further displaced. The red outlines show the condition of these partial rollers `a-t the end of each movement of the valve.

The steam is admitted to the ports in the cylinder through .the passages a a and b b in the respective parts A B. These passages are arranged as represented so that the part A may slide vertically upon B and vice versa Without closing the .passages a or dividing line.

In commencing to operate my valve the set Vscrews C C are slackened and the part A is thus allowed to be pressed down Vinto steam-tight Contact With the cylinder face M by the pressure of `the steamon that part of A which is not protected therefrom 'by B. VIt is Worked for several days in this condition so that it is :tree to rise and sink Without alecting B and 'is then (either at a single operation or xby gradually increasing the tightness at several operations set firmly in relation to B 'by turning lthe set screws 'C C, in which case it continues to "lit tightly upon the cylinder face M by reason that the mot-ion of B is parallel thereto.

It will readily be seen that my invention is Ycapable of being constructed in various forms and proportions other than .those which I have here represented. For eX- ample any varietyof cut-ofi'l vdevice Which is suitable Y,to Work on the back or Within the body of other slide valves may be employed in my invention as 'the valve D instead of the precise form and proportion which I have represented. Broad heads may also be forged on the pins B vand M" Which pins may be threaded l,and tapped into the respective parts so as to become bolts, and thus a lateral play vof the` partial rollers E may be prevented Vby the heads of these bolts in lieu of Dby the lips represented. Many other modifications may readily be "adopted Without varying substantially from respective positions substantially in the mannerV and forr the purposes herein set f0rth. i

2. I Clo-.not claim the employment of a cut o'ff valve D sliding on the back of a valve having passages a b 4through which the'steam .is admitted to the ports in the cylinder under the control of iboth valves, but I claim the Within described arrangement of the supported back piece B loose seV 10 within described method of adjusting the parts A B relatively to each other that isto say working the parts A B for al period in a free relation and then tightening the union by the set screws C C or their equivalents until it becomes rigid substantially 15 as herein shown and described.

R. C. BRISTOL. Witnesses:

SAM T. ATWATER, JAS. VAN INWAGEN. 

